Earplugs are used to prevent entry of foreign material, especially water, into the ear canal. They are also used to prevent or reduce entry of sound waves, thereby providing auditory protection or assisting the wearer in sleeping. Such plugs are usually designed to fit into the ear canal to be engaged more or less tightly by the wall of the canal inside the entrance area thereof to frictionally hold the plug in place. They remain in place because they are wedged into the ear canal, and they tend to leak, fall out or irritate the canal because of the wedge pressure.
In addition to these well known types of rubber or foamed plastic plugs that are designed for frictionally engaging the walls of the canal, there are other kinds of plugs such as one made of a putty-like silicone resin body shaped into a form for insertion into the canal to form an earplug, the resin being encased in a flexible envelope to aid its insertion into the canal where it likewise is held in place by frictional engagement with the wall of the canal. This type of earplug is described in U.S. Pat. No. 3,771,521.
Another somewhat similar plug is shown in U.S. Pat. No. 4,160,449, where a foam plastic encased in a thin flexible envelope is utilized to hold the foam compressed during insertion into the canal, the compressed foam being released upon insertion in the canal to expand and engage the wall of the canal.
As an alternative to a plug engaged within the ear canal, U.S. Pat. No. 4,134,153 discloses a bag-like structure for enclosing the entire ear. The bag is attached to the head with a pressure sensitive adhesive. U.S. Pat. No. 2,574,288 discloses an ear protector in the form of a wax body which spans the entrance to the ear canal and when lightly pressed in place by a finger becomes slightly softened by the heat of the flesh and conforms itself to the shape of the part of the ear against which it has been pressed.
All of these known means have defects in use and are either uncomfortable to wear over long periods of time or do not, in the case of the bag-type seal, provide a very effective seal. Swimmers may move through the water rapidly or may be subjected to rough treatment by breakers during ocean bathing and such vigorous water action may wash away frictionally held plugs or the bag-type of ear enclosure. Further, if the more popular frictionally supported plugs are used during periods of highly active swimming and diving for example, the plugs must be tightly engaged in the ear canal and soon become very uncomfortable to wear.
My U.S. Pat. No. 4,344,425 discloses improvements over the earlier earplugs.